An Army inside a Stronghold under siege may attack the besieging Army by using an Action die for battle during the Action Resolution phase.
A battle in which the attacker is under siege is called a sortie.
In a sortie, the besieged Army fights a field battle for at least one round, forfeiting the advantages of defending the Stronghold.
A rearguard may be formed and left behind in the Stronghold.
Combat is resolved normally (with both Armies scoring hits on a ‘5’ or higher) but, if the attacker wants to cease the battle, the attacking Army moves back into the Stronghold.
The besieging defending Army may retreat to a free adjacent region as usual.
If the attacking Army wins the sortie, it cannot advance outside of the region.